The present application claims priority to Japanese Application No. P11-176008 filed Jun. 22, 1999 which application is incorporated herein by reference to the extent permitted by low.
1. Field of the Invention
The present invention relates to a nonaqueous electrolyte batter incorporating a positive electrode, a negative electrode and a nonaqueous electrolyte.
2. Description of the Related Art
Hitherto, a nickel-cadmium battery, a lead battery or the like has been employed as a secondary battery for an electronic apparatus. Since the electronic technology has been developed in recent years, the size of the electronic apparatus has been reduced and a portable structure of the same has been employed. Therefore, raising of the energy density of the secondary battery for the electronic apparatus has been required. The nickel-cadmium battery and the lead battery suffer from unsatisfactorily low discharge voltage. Thus, a sufficiently high energy density cannot be obtained.
Therefore, so-called lithium-ion batteries have energetically been researched and developed. The lithium-ion battery is characterized in a long life against cycle operations because of a high discharge voltage and a small spontaneous discharge. The lithium-ion battery is a nonaqueous electrolyte battery incorporating a negative electrode constituted by a carbon material which pennits doping/dedoping of lithium ions. The positive electrode of the lithium-ion battery is constituted by lithium transition metal oxide expressed by general formula LiMxOy (where M is at least of one material selected from Co, Ni, Mn, Fe, Al, V and Ti).
In the lithium battery, lithium ions are discharged from the positive electrode owing to discharge. Lithium ions above are inserted into gaps of carbon in the negative electrode so that a compound with carbon is produced. The foregoing phenomenon is called a xe2x80x9cdoping phenomenonxe2x80x9d. When the discharge is plastic film, lithium in the negative electrode is formed into lithium ions. Lithium ions are discharged from carbon so as to be returned to LiMxOy. The foregoing phenomenon is called a xe2x80x9cdedoping phenomenonxe2x80x9d. That is, the lithium-ion battery generates electric energy owing to movement of lithium ions. The . nonaqueous electrolytic solution considerably concerns the movement of lithium ions. Note that the nonaqueous electrolytic solution is one of nonaqueous electrolytes.
To improve the characteristics of the nonaqueous electrolyte battery including the internal resistance of the battery and the initial capacity, the characteristics of the nonaqueous electrolytic solution for moving lithium ions are as well as important factors as well as the characteristics of the positive electrode and the negative electrode.
The nonaqueous electrolytic solution is exemplified by propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethylcarbonate, methylethyl carbonate and diethyl carbonate. The nonaqueous electrolytic solution prepared by mixing the foregoing materials permits a high dielectric constant to be obtained, causing the characteristics of the battery to be improved. Therefore, the nonaqueous electrolytic solution has widely been used.
In recent years, a battery which can be used even in an environment (hereinafter simply called a xe2x80x9cheavy load environmentxe2x80x9d) in which great energy is used has been required. That is, the characteristics of the battery (hereinafter called a xe2x80x9cheavy load characteristicsxe2x80x9d) in a heavy load environment must be improved. To improve the heavy load characteristics, also the composition of the nonaqueous electrolytic solution and the like must furthermore be investigated.
In view of the foregoing, an object of the present invention is to provide a nonaqueous electrolyte battery exhibiting satisfactory heavy load characteristics.
To achieve the foregoing object, according to one aspect of the invention, there is provided a nonaqueous electrolyte battery comprising: a negative electrode constituted by a material which permits doping/dedoping of lithium ions; a positive electrode constituted by a material containing lithium; and a nonaqueous electrolyte, wherein the nonaqueous electrolyte contains vinylene carbonate expressed by chemical formula 1: 
The nonaqueous electrolyte battery according to the present invention and structured as described above is capable of decreasing the internal resistance to enlarge the initial capacity. Thus, the heavy load characteristics can be improved.